The claimed invention relates to a method of preparing recoatable surfaces which have been imaged with sublimatable inks. Specifically, the claimed invention is directed to methods of forming UV-cured coatings on substrates which are then imaged with a sublimation dye. Advantageously, the imaged surface is recoatable and receptive to the application of a top coat or stain over the sublimated dye image.
There is a discernible and growing market demand, particularly in the furniture industry, for decorated substrates that can be recoated to satisfy a manufacturing requirement or individual preference. In addition to wood, such substrates may include but are not limited to glass, plastic, metal and canvas. It is generally known that certain substrates can be decorated by applying a transfer sheet printed with a selected design, bringing the decorated transfer sheet into contact with a substrate, and by the application of heat and pressure, transferring the decoration from the transfer sheet to the surface of the substrate. It is also known that by using sublimation dyes which vaporize when heated, the decoration can be made to penetrate or bleed into the body of the substrate.
However, the surfaces of materials such as glass and wood are not as receptive as other substances, such as paper, to the printing of decorations directly onto their surfaces. Decorative elements printed directly on these types of substrates are prone to abrasion and wear. In addition, exposure of an imaged object to sunlight or UV-light can cause the sublimation dyes to fade, thereby reducing the visual attraction of the object.
In order to decrease the fading of an sublimated dye image, the surface of an object which has been subjected to sublimation can be coated with a protective layer or top coat. Alternatively, a clear film such a polypropylene film can be applied with heat and pressure to the surface of the imaged article. However, applying such a coating requires an additional processing step, which increases costs and manufacturing cycle times.
In accordance with U.S. Pat. No. 6,242,055, a radiation curable coating containing compounds which provide UV protection is applied to the surface of a substrate. The preferred coating is a urethane acrylate/polyester acrylate blend with additives such as UV absorbers and hindered amine light stabilizers. The radiation curable coating is subjected to a curing step with an electron beam, ultraviolet radiation beam or both. Subsequently, a sublimation ink is transferred to the radiation-cured coating.
Since it is the express purpose of U.S. Pat. No. 6,242,055 to eliminate the addition of a clear film coating over the sublimated image, there is no disclose or suggestion of the desirability of applying an additional top coat or layer to further protect or alter the final appearance of the imaged article. As such, there is no appreciation by U.S. Pat. No. 6,242,055 of the properties and composition of a UV curable film composition that both accepts sublimatable inks and is afterwards receptive to subsequent finishes or stains altering or enhancing the imaged surface.
Therefore, there is a continuing need to prepare UV stabilized substrates that are capable of accepting sublimatable inks wherein the surface of the imaged article is advantageously receptive to a subsequent stain or top coat which adheres uniformly and does not run off. As a result, it is possible to adjust the final coloration or appearance of the imaged article to satisfy limitless commercial applications and personal preferences. None of the known methods of coating substrates permit the ready preparation of a transparent, UV-cured coating which is imaged by a sublimation dye and which is receptive to a top coat or stain.
The present invention relates to a method for preparing a recoatable substrate which has a sublimation dye image transferred into the surface of the substrate and which is receptive to a subsequent top coating. By recoatable, it is meant that the surface of the cured and imaged article will accept a further top coating step such as an additional finish or strain which adheres uniformly to the imaged surface and does not run off.
It has been surprising discovered that a recoatable surface is obtained when a base coat composition comprising a polyol acrylate monomer and an epoxy acrylate monomer is applied to a substrate and cured by UV radiation. The base coat material penetrates and tightly bonds with the surface of the substrate after curing by UV radiation. The base coat is subsequently imaged with a sublimation dye design. The imaged design does not need to extend over the entire surface of the article and, therefore, unimaged areas remain transparent and showing the natural surface and coloration of the substrate. The imaged base coat can optionally be stained or colored with a top coat after the sublimation dye design has been transferred to the base coat.
Substrates which can be used with the present invention include, but are not limited to wood, glass, plastic, canvas, and non-woven polyester. Wooden substrates formed from natural wood, engineered wood, untreated or treated wood, particle board, and pressed wood may all be successfully coated with the claimed method. In accordance with the claimed invention, even substances such as glass which are not typically considered porous can be successfully coated and imaged. Glass or plastic substrates which are coated and imaged retain their light-transmitting properties and thereby permit a substantial amount of light to pass through the glass. The present invention has particular application to the furniture and decorative arts industries.